isCnpj static method

bool isCnpj(String cnpj)

Implementation

static bool isCnpj(String cnpj) {
  // Get only the numbers from the CNPJ
  final numbers = cnpj.replaceAll(RegExp(r'[^0-9]'), '');

  // Test if the CNPJ has 14 digits
  if (numbers.length != 14) {
    return false;
  }

  // Test if all digits of the CNPJ are the same
  if (RegExp(r'^(\d)\1*$').hasMatch(numbers)) {
    return false;
  }

  // Divide digits
  final digits = numbers.split('').map(int.parse).toList();

  // Calculate the first check digit
  var calcDv1 = 0;
  var j = 0;
  for (var i in Iterable<int>.generate(12, (i) => i < 4 ? 5 - i : 13 - i)) {
    calcDv1 += digits[j++] * i;
  }
  calcDv1 %= 11;
  final dv1 = calcDv1 < 2 ? 0 : 11 - calcDv1;

  // Test the first check digit
  if (digits[12] != dv1) {
    return false;
  }

  // Calculate the second check digit
  var calcDv2 = 0;
  j = 0;
  for (var i in Iterable<int>.generate(13, (i) => i < 5 ? 6 - i : 14 - i)) {
    calcDv2 += digits[j++] * i;
  }
  calcDv2 %= 11;
  final dv2 = calcDv2 < 2 ? 0 : 11 - calcDv2;

  // Test the second check digit
  if (digits[13] != dv2) {
    return false;
  }

  return true;
}